This invention relates generally to wristwatches driven by a stepping motor, and more particularly to a very thin wristwatch having a reduced number of components.
Stepping motor watches are known with conventional hour and minute hands driven by a stepping motor rotor, which periodically advances in response to electrical pulses. The pulses may be provided by an integrated circuit having a quartz oscillator time base. An exemplary patent of a stepping motor watch is shown in my U.S. Pat. No. 4,249,251 issued Feb. 3, 1981 and assigned to the present assignee.
Wristwatches of reduced thickness have been proposed, in which the hour hand and minute hand are painted or embossed on rotating discs which are driven at the periphery by a stepping motor, through an intermediate gear train, at least the upper disc being transparent. Such constructions are shown in published U.K. Patent Application No. GB 2050654A, assigned to Societe Suisse Pour L'Industrie Horologere Management Services, published Jan. 7, 1981, and No. GB 2056126A, assigned to Ebauches SA, published Mar. 11, 1981. While these patents provide wristwatches of reduced thickness, it is necessary to locate the components of the watch such as stepping motor, gear train, battery, quartz crystal and integrated circuit to either end of the watch outside of the periphery of the discs, thereby somewhat increasing its overall dimensions in return for its reduced thickness. Other patents showing timepieces which replace the hands by indicating discs are shown in Swiss Pat. No. 307,045 and in German Laid Open Application Nos. 2204907 and 2548559.
The use of discs driven at their periphery as a substitute for conventional time indicating hands offers certain possibilities to reduce the thickness of the timepiece. However, most constructions utilizing a disc have employed a transparent disc either with one or more conventional hands or another disc below it. A transparent disc removes any possibility of hiding watch components beneath it and hence they must be placed beyond the periphery of the disc, thereby increasing the overall size of the timepiece.
It is also necessary to control the axial movement or "endshake" or rotating parts, and to provide various electrically conductive elements. It would be desirable to have a very thin timepiece, which employs a minimum number of parts. The timepiece should be easy to assemble and the various components of the timepiece should perform multiple functions, both mechanical and electrical whenever possible, in order to reduce the cost and provide a more reliable timepiece.
Accordingly, one object of the present invention is to provide a thin wristwatch driven by a stepping motor.
Another object of the invention is to provide a thin wristwatch with a reduced number of components.